Modeling Earth, Fluids, Plasmas and Space (2026/2027)
Organizers: Ludovic Ferrière (WPI c/o NHM Abu Dhabi), PF Rupert Klein (FU Berlin),
Caroline Muller (WPI c/o ISTA), Marco di Paoli (WPI c/o TU Wien), PF Alex Schekochihin (Oxford), Glen van de Ven (WPI c/o U.Wien), Bernadett Weinzierl (WPI c/o U.Wien)
Talks
| Uriel Frisch |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Thu, 8. Oct 26, 10:20 |
| Large-scale multifractality for Burgers and Navier-Stokes |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Takeshi Matsumoto |
online |
Thu, 8. Oct 26, 11:10 |
| Large-scale multifractality in decaying turbulence in the Sabra shell model |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Dario Vincenzi (U. Côte d’Azur) |
WPI Seminar room, 8th floor Fak.Math. U. Wien |
Thu, 8. Oct 26, 14:45 |
| Dissipation regimes in Navier-Stokes turbulence |
Numerical simulations inspired by the renormalization-group approach and experiments of fractal-grid turbulence have shown that the phenomenology of turbulence is sensitive to the features of the forcing that sustains the flow. After a brief review of the known results in three dimensions, I will discuss how dissipation-rates estimates depend on the forcing function in the two-dimensional body-forced Navier-Stokes equations and the helical-decimated Navier-Stokes equations.
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- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Pierre Germain (U. Wien) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Thu, 8. Oct 26, 15:30 |
| Weak turbulence |
Wave, or weak, turbulence refers to the turbulent regime for which wave or dispersive effects are dominant over nonlinear effects. The mathematical theory of wave turbulence has recently seen tremendous progress, which was in particular acknowledged by the Fields Medal awarded to Yu Deng. I will try and present the field quickly, emphasizing the common features as well as the differences with classical (strong) turbulence. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Francois Golse (École Polytechnique) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Fri, 9. Oct 26, 10:10 |
| A Nonlinear Regularization Mechanism for the Inviscid Burgers Equation |
It is well-known that the nonlinearity in the inviscid Burgers equation
is the reason for the onset of shock waves in finite time starting from
smooth, compactly supported initial data.
On the other hand, it is known since the work of Lax in 1954 that the
semigroup of entropies solutions to the inviscid Burgers equations is L^1
compact, which suggests that this equation also has some regularizing effect based on the nonlinearity and the entropy condition. The talk will discuss some ideas explaining this
mechanism.
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- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Yann Brenier (CNRS Paris) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Fri, 9. Oct 26, 11:10 |
| Burgers and gravitation |
The link between gravitation theory and the Burgers equation was emphasized in many works of Uriel in connection with Zeldovich’ approximation in the modeling of the early universe. A striking point for me was Uriel’s key observation that the reconstruction of the early universe could be formulated as an optimal transport problem. Recently, I established a reformulation of Einstein’s equations in vacuum as a matrix valued generalization of the Burgers equation. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Oliver Hahn (U. Wien) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Fri, 9. Oct 26, 11:50 |
| Reconstructing the Universe’s Devil’s Staircase |
Uriel Frisch made important contributions to large-scale structure cosmology, including Burgers dynamics in the adhesion model of cosmic structure, optimal-transport reconstruction of the early Universe, and the time-analyticity of Lagrangian trajectories. I will give a brief visual review of the first two, then discuss how aspects of all three connect to the most recent efforts in large-scale structure cosmology, as it confronts data of unprecedented quantity and quality.
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- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Cornelius Rampf (Inst. Ruder Boskovic) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Fri, 9. Oct 26, 14:00 |
| Cosmological fluid flow: from singularities to optimized numerical schemes |
On large cosmological scales, cold dark matter can accumulate efficiently in regions of gravitational collapse, giving rise to the highly nonlinear, filamentary network of cosmic large-scale structure. Traditionally, the dynamics of dark matter have been studied primarily through numerical simulations, while analytical approaches were often regarded as approximate tools for obtaining qualitative insights.
In this talk, I show how Uriel’s methods on singularities and their detection have helped transform our understanding of cosmic structure formation. In particular, I discuss how singularity analysis led to the first blow-up solutions in three dimensions and, ultimately, to improved numerical schemes for cosmological fluid dynamics. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Rahul Pandit (Indian Inst. of Science) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Fri, 9. Oct 26, 15:10 |
| Uncovering finite-time singularities in incompressible 3D magnetohydrodynamics |
We provide compelling numerical evidence for the development of (potential) finite-time singularities in the three-dimensional axisymmetric, ideal, incompressible magnetohydro- dynamic (IMHD) equations, in a wall-bounded cylindrical domain, starting from smooth initial data, for the velocity and magnetic fields. We demonstrate that the nature of the singularity depends crucially on the relative strength C of the velocity and magnetic fields at the time of initialization. If time permits, we will examine the implications of the OpenAI preprint on a 3D Navier-Stokes singularity for 3D MHD. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Luca Biferale (U. Roma) |
WPI Seminar room, 8th floor Fak.Math. U. Wien |
Sat, 10. Oct 26, 10:10 |
| Generative AI vs Uriel: Who Stirs Up More Turbulence? |
We introduce a stochastic generative framework for the reconstruction and augmentation of complex, multiscale signals arising in Eulerian and Lagrangian turbulence. The approach builds on generative Diffusion Models, a class of probabilistic deep learning methods capable of learning high-dimensional data distributions beyond Gaussian approximations. We also briefly discuss signals generation using fully interpretable Moment Guiding Techniques converging towards maximum-Entropy distribution and apply it to Burgers signals and to 1D signals of 3D turbulence along Lagrangian trajectories. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|
| Samriddhi Sankar Ray (ICTS Bangalore) |
WPI Seminar room, 8th floor Fak.Math. Univ. Wien |
Sat, 10. Oct 26, 10:55 |
| Dynamical slowdown, bottlenecks, and multiscaling in Voigt-regularised turbulence |
Dynamical slowdown, bottlenecks, and multiscaling in Voigt-regularised turbulence are studied using the Voigt-SABRA shell model and Navier-Stokes-Voigt simulations.
Voigt regularisation introduces a scale-dependent slowdown of nonlinear interactions without directly increasing dissipation.
Three spectral regimes are observed: a Kolmogorov inertial range, an intermediate equilibrium-like range, and a high-wavenumber equilibrium range.
The bottleneck develops due to the progressive weakening of the forward energy cascade at smaller scales.
The high-wavenumber crossover occurs at a scale proportional to alpha^(-1).
Increasing alpha delays cascade completion and enhances energy accumulation at intermediate and small scales.
The study finds reduced intermittency and increasingly Gaussian statistics with stronger Voigt regularisation.
Dynamic multiscaling in the turbulent regime changes to simple scaling in the equilibrium-like regimes.
Both shell-model and DNS results show bottleneck formation, delayed cascade, and reduced small-scale intermittency.
The findings suggest that bottlenecks are associated with scale-dependent dynamical slowdown and incipient thermalisation rather than purely dissipative effects. |
- Thematic program: Modeling Earth, Fluids, Plasmas and Space (2026/2027)
- Event: Uriel85Fest: Workshop "Around Burgers";
in honour of the 85th birthday of Uriel Frisch (2026)
|